Various approaches have been taken to reduce or eliminate the risks associated with patients having implanted medical devices who need magnetic resonance imaging (MRI) examinations.
However, the specific characteristics and requirements of defibrillator systems create unique challenges. Unlike pacemaker, drug pump, and neurostimulation devices, implantable cardioverter defibrillators (ICDs) not only sense and pace the heart in a manner similar to a pacemaker, but also may release electrical energy in pulses of up to 40 Joules and at an excess of 800 volts and 10 amps if ventricular fibrillation (VF) or other anomalous conditions are sensed.
While this may occur very rarely, prior art solutions to thermogenic tissue risks associated with the radio frequency (RF) fields used in magnetic resonance imaging in some cases utilize small electrical components that can be damaged in the presence of electrical potentials and currents of this magnitude. Specifically, the miniature inductive, capacitive, and semiconductor components that may be packaged in the electrode assembly of a pacemaker lead are typically rated for potential and current levels far below those used in defibrillation.
Thus, it is desirable to provide a defibrillation electrode that enables highly reliable operations over the life of the ICD implant in a patient, but such that when the patient is placed in the bore of a magnetic resonance imaging system, all sources of RF-induced energy and gradient-field-induced energy that could harm the patient are totally isolated electrically, thus providing complete safety for the patient.